external wastegate question

[shinny]

I'm not sure I follow here..

I guess it's A-level physics (F=PA)... the long and short of it that the pressure difference pre and post turbo would have to be a good few times higher than the cracking pressure, assuming the actuator diaphragm is significantly larger than the wastegate, which it appears to be on the CT26.

BTW, I wasn't suggesting an exhaust would see 1bar backpressure... most certainly not on a 3" straight through exhaust! I picked a very high figure because that makes the numbers more likely to be able to open the wastegate on exhaust pressure alone. But still the figures don't appear to add up.

why introduce another potential point of failure into the system when you can just weld it up and be done with it

I think I've already explained why I wish I hadn't had mine welded up and why I expect a disconnected actuator will be sufficient to hold the wastegate shut.

I guess it's a choice between "absolutely sure" and "flexible" / "resale value". The latter would have been much more useful to me! (And that has nothing to do with the poorly designed dump pipe on my GT28 kit)

[2mad]

If creeps the problem and you have money for tools and some free time why not port the wastegate. I did my ct20b and it only crept 0.1bar over my boost setting afterwards (eg. 0.9bar on my boost controller got me 1.0bar), i was very happy.
I had a 3"downpipe and mongoose free flow exhaust.

Can post pics of the process if interested

[shinny]

If creeps the problem and you have money for tools and some free time why not port the wastegate. I did my ct20b and it only crept 0.1bar over my boost setting afterwards (eg. 0.9bar on my boost controller got me 1.0bar), i was very happy.
I had a 3"downpipe and mongoose free flow exhaust.

Can post pics of the process if interested

I'm not sure I'd consider the target figure on a boost controller as significant for much TBH. The simplest way for checking for boost is to run no boost control and see if boost stays at actuator pressure or whether it rises at higher RPM.

I tried a ported wastegate on a CT20b between my second and third external wastegate setups. I would still hit fuel cut at about 6000rpm while on actuator pressure... although my car appears to be a creep machine for no apparent reason

[2mad]

If creeps the problem and you have money for tools and some free time why not port the wastegate. I did my ct20b and it only crept 0.1bar over my boost setting afterwards (eg. 0.9bar on my boost controller got me 1.0bar), i was very happy.
I had a 3"downpipe and mongoose free flow exhaust.

Can post pics of the process if interested

I'm not sure I'd consider the target figure on a boost controller as significant for much TBH. The simplest way for checking for boost is to run no boost control and see if boost stays at actuator pressure or whether it rises at higher RPM.

I tried a ported wastegate on a CT20b between my second and third external wastegate setups. I would still hit fuel cut at about 6000rpm while on actuator pressure... although my car appears to be a creep machine for no apparent reason

I had a fensport turbo actuator (very nice bit of kit, dont know who made it) and it was 7psi rock steady on my ported ct20b to the redline.. with boost control it was 0.1bar out, no biggy


I did port the funk out of it .. took best part of a weekend

[shinny]

I had a fensport turbo actuator (very nice bit of kit, dont know who made it) and it was 7psi rock steady on my ported ct20b to the redline.. with boost control it was 0.1bar out, no biggy


I did port the funk out of it .. took best part of a weekend

That's the thing - porting works great for some people and not others. I also remember reading reports of GT4 owners (who seem to suffer from creep more anyhow) cracking turbine housings after getting enthusiastic porting their wastegates. However, as with all things on the internet, there are probably plenty more for whom it worked just fine.

I don't blame Dylan for considering an external gate because, done right, it is easily the best bet of sorting out creep once and for all

[dylan5084]

Haha, not trying to sell it man, just trying to help you out. There is twin scroll adapters available, one thing i didn't think about was oil and water lines. I'm not sure where the turbo would sit with that manifold i have, you would need the t3 adapter as i said. It's a lot of mucking about so it depends on how much benefit you'd see from the external gate.

It would be good to get some sort of measurement on the depth of the pipe, as it looks quite deep in the pic from flange face to end of the pipe, if you get me?

[Ryan S]

I have it in my possesion now so you're more than welcome to come take a look at it if you want

[dylan5084]

Got a shed to go and dismantle today, might take you up on that later on, pm me your address again mate

[2mad]

I had a fensport turbo actuator (very nice bit of kit, dont know who made it) and it was 7psi rock steady on my ported ct20b to the redline.. with boost control it was 0.1bar out, no biggy


I did port the funk out of it .. took best part of a weekend

That's the thing - porting works great for some people and not others. I also remember reading reports of GT4 owners (who seem to suffer from creep more anyhow) cracking turbine housings after getting enthusiastic porting their wastegates. However, as with all things on the internet, there are probably plenty more for whom it worked just fine.

I don't blame Dylan for considering an external gate because, done right, it is easily the best bet of sorting out creep once and for all

Exactly.. I would never say do as i did and it will work .. to many variables.. i was probably lucky

[Ryan S]

Got a shed to go and dismantle today, might take you up on that later on, pm me your address again mate

No probs man, I'm busy tonight and away out on the bike camping over the weekend but I'll be back sunday, I'll fire you my address

[C35Rob]

I'm not sure I follow here..

I guess it's A-level physics (F=PA)

I didn't mean I didn't understand, it's handy being a marine engineer on a nuclear submarine, studying reactor physics and what not what I meant, politely, is your examples were, imo, wrong.

I've seen many EWG conversions, none have ever left the actuator in place.. but if it works for you then, well.. it's your car.

[dylan5084]

So I had sneaking suspisions that My manifold had cracked, so I've took off the heat wrap, some of the heat wrap had turned into glass... Pretty hot! and yep it is cracked so I'll defo take your manifold mate

means I can cut off the flange of both and weld my one into the other without feeling like I've wasted money that could have been recouped from selling the old manifold

Just won A tial wastegate on eBay too so it seals the deal for me

I'll weld the old one just now so I can still use the car, as the crack is accessible from to top anyway

[shinny]

I'm not sure I follow here..

I guess it's A-level physics (F=PA)

I didn't mean I didn't understand, it's handy being a marine engineer on a nuclear submarine, studying reactor physics and what not what I meant, politely, is your examples were, imo, wrong.

Sorry, I have no idea of your background (just as you have no idea about mine) but you didn't counter my theoretical pondering so I interpreted your comment as "I didn't understand". (That could still mean I didn't explain myself well, rather than imply a lack of ability on your end) You said the pressure in the exhaust manifold is probably more than the boost pressure. My point was that, for the CT26, it would have to be at least triple the cracking pressure (relative to the pressure in the exhaust, not the atmosphere) to make it actually move.

I've seen many EWG conversions, none have ever left the actuator in place..

Just because everyone does the welding doesn't mean it's actually necessary!

I'd be very interested in either some solid theory to say the pressure is actually high enough to push open the flap or a counter example of someone who's tried it. There are so many urban myths going round the modified car scene that I often choose to question the "accepted wisdom" because sometimes it makes no sense what-so-ever.

but if it works for you then, well.. it's your car.

I've not run this setup on my car... I wish I had, as I'd be a few £100 better off as I'd be able to sell my spare CT20b!

However I'm in the rare position of being able to easily try it, albeit with a Garrett actuator rather than Toyota. Looking at the diaphragm housing of each, I'd suggest the Garrett unit would crack easier (smaller diagram = less force for a given boost pressure = weaker spring = lower exhaust pressure required to lift the flap), but either way it's a test we can actually do, rather than just disagreeing on theory

I can easily disconnect the internal gate's vac hose and leave the external gate connected. What I don't immediately know is how to know if the actuator moved or not. Some options would be:
1) Mount both a light and a (cheap) camera in the engine bay
2) Remove the engine cover and mount a GoPro on the rear glass
3) Put a circlip on the actuator arm and fashion some form of guide that will push the circlip back along the arm should the wastegate move

Then we'll have actually have an experimental answer as to whether the internal gate actually does get blown open or not. I might prove myself wrong, which would be fine... at least there would be some solid evidence instead of "that's what everyone else does".

[dylan5084]

I guess it's A-level physics (F=PA)

I didn't mean I didn't understand, it's handy being a marine engineer on a nuclear submarine, studying reactor physics and what not what I meant, politely, is your examples were, imo, wrong.

Sorry, I have no idea of your background (just as you have no idea about mine) but you didn't counter my theoretical pondering so I interpreted your comment as "I didn't understand". (That could still mean I didn't explain myself well, rather than imply a lack of ability on your end) You said the pressure in the exhaust manifold is probably more than the boost pressure. My point was that, for the CT26, it would have to be at least triple the cracking pressure (relative to the pressure in the exhaust, not the atmosphere) to make it actually move.

I've seen many EWG conversions, none have ever left the actuator in place..

Just because everyone does the welding doesn't mean it's actually necessary!

I'd be very interested in either some solid theory to say the pressure is actually high enough to push open the flap or a counter example of someone who's tried it. There are so many urban myths going round the modified car scene that I often choose to question the "accepted wisdom" because sometimes it makes no sense what-so-ever.

but if it works for you then, well.. it's your car.

I've not run this setup on my car... I wish I had, as I'd be a few £100 better off as I'd be able to sell my spare CT20b!

However I'm in the rare position of being able to easily try it, albeit with a Garrett actuator rather than Toyota. Looking at the diaphragm housing of each, I'd suggest the Garrett unit would crack easier (smaller diagram = weaker spring = less force required on the arm), but either way it's a test we can actually do, rather than just disagreeing on theory

I can easily disconnect the internal gate's vac hose and leave the external gate connected. What I don't immediately know is how to know if the actuator moved or not. Some options would be:
1) Mount both a light and a (cheap) camera in the engine bay
2) Remove the engine cover and mount a GoPro on the rear glass
3) Put a circlip on the actuator arm and fashion some form of guide that will push the circlip back along the arm should the wastegate move

Then we'll have actually have an experimental answer as to whether the internal gate actually does get blown open or not.

Sounds like a plan, and it would (hopefully) mean I don't need to weld up my turbo!

[Ryan S]

I don't know if this has been said but could you not simply weld the actuator in place to keep the wastegate flap closed? That way you could just replace the actuator if needed rather than destroy an exhaust housing by welding it?

[shinny]

I don't know if this has been said but could you not simply weld the actuator in place to keep the wastegate flap closed? That way you could just replace the actuator if needed rather than destroy an exhaust housing by welding it?

If you don't weld the wastegate then you ideally want to keep pressure on the flap to keep it shut. If you weld the actuator arm fractionally too long you'll always have the flap cracked open a tiny bit. If you weld the actuator arm fractionally too short, you'll have an almighty task getting the actuator back onto the turbo in the first place!

[dylan5084]

Would pushing the internal wastegate open cause it to boost creep? Or just slow the boost building, I'd be happy if I just eliminated boost creep to be honest, although a properly working setup would be great! Welding the actuator sounds a good idea

[dylan5084]

Wouldn't a couple of small tack welds on the wastegate hold it, and then it would just take a grinder, or burr to take out the welds and its sorted?

[C35Rob]

if you're set on not welding the poppet valve shut, you could remove the actuator and bracket and fabricate a new bracket to which you could attach a threaded rod, so that you could mechanically hold the poppet valve shut, whilst maintaining a degree of adjustment to ensure the valve is seated correctly

having the valve open, or anywhere other than shut will delay the boost building, cause your turbo to work harder to produce the same amount of boost (and therefore you'll have hotter charge temps) boost creep is caused because the turbo speed cannot be regulated (i.e gas diverted from the turbine) efficiently - this could be due to a faulty actuator, the poppet valve being too small, or not opening properly, the turbine wheel and or housing being too small among other things. The boost creep is a symptom of a larger problem.

also, a big downside of the IWG is that it dumps its gas into the flow of the turbine, which causes more of a restriction in getting the gas through the turbo and out the exhaust.. add to that, with an EWG the dumped gas doesn't have to share the downpipe (in the case of having a screamer) or at least the flows merge further down the system where it will not be as much of a restriction - win/win.

[shinny]

Would pushing the internal wastegate open cause it to boost creep? Or just slow the boost building, I'd be happy if I just eliminated boost creep to be honest, although a properly working setup would be great! Welding the actuator sounds a good idea

If the internal gate cracks open you'll build boost slower. That's about it.

Wouldn't a couple of small tack welds on the wastegate hold it, and then it would just take a grinder, or burr to take out the welds and its sorted?

I'm not a welding expert by any stretch of the imagination, but I'd guess that the welds won't hold very long. You flow some very hot gasses through the turbo and I'd expect the expansion and contraction of the wastegate flap at different rates to the turbine housing would pop a couple of tack welds in short order.